The alcohols of long chain olefins having about 10 to 28 carbon atoms have considerable commercial importance in a variety of applications, including detergents, soaps, surfactants, and freeze point depressants in lubricating oils. These alcohols are produced by any one of commercial processes, such as the oxo or hydroformylation of long chain olefins. Typical long chain alcohols are the commercially available NEODOL® alcohols made by Shell Chemical Company, the EXXAL® alcohols available from Exxon Chemical, and the LIAL® alcohols available from Enichem.
In the manufacture of the NEODOL® alcohols, a predominantly linear olefin feed is subjected to hydroformylation by reacting carbon monoxide and hydrogen onto the olefin in the presence of an Oxo catalyst to form an alcohol. In excess of 80% of the number of alcohol molecules in the resultant alcohol composition are linear primary alcohols. Of the branched primary alcohols in the composition, substantially all, if not all, of the branching is on the C2 carbon atom relative to the hydroxyl bearing carbon atom. These alcohols can subsequently be converted to anionic or nonionic detergents or general surfactants by sulfonation or ethoxylation, respectively, of the alcohol. Also known as anionic surfactants for detergents are the alcohol-ethoxysulfates.
The NEODOL® line of alcohols has met with considerable commercial success with detergents because the NEODOL® alcohol compositions can be economically produced with high yields of linear alcohols. The desire to use linear alcohols as intermediates for detergent grade surfactants exists because it is generally recognized that linear alcohols biodegrade, while the branched long chain alcohol sulfonates exhibit poor biodegradability. Since detergents and soaps used by consumers for washing are ultimately released into the environment, the need to provide a surfactant or detergent which biodegrades is well recognized.
For example, U.S. Pat. No. 5,112,519 describes the manufacture of a surfactant by oligomerizing C3 and C4 olefins through a surface deactivated ZSM-23 catalyst to form oligomers, hydroformylating the oligomer, and recovering a semi-linear alcohol composition having less than 1.4 methyl branches, and whose branching is limited to methyl branches. The alcohol can be ethoxylated and/or sulfated and is reported to be biodegradable, and further have improved low temperature properties compared to isotridecyl alcohol. Retaining the linearity of the alcohol composition to less than 1.4, along with obtaining methyl branching were important considerations to achieving a biodegradable surfactant. It would be desirable, however, to obtain a biodegradable surfactant without limiting the branching to methyl branches, without limiting the branching to under 1.4, and without limiting oneself to a ZSM 23 surface deactivated catalyst. It would also be desirable to make a biodegradable surfactant without conducting oligomerization reactions through zeolite catalysts, which are expensive and may coke up or be used up quickly if one needs to build chain length through the catalyst.
Another product, EXXAL® 13, is derived from propylene oligomerization through acid catalysis to a wide range of mono-olefins, the range having an average of C13s being distilled out, but containing some olefins in the C10-15 range. The olefin is then subjected to hydroformylation using an oxo process. EXXAL® 13 is reported to be a 3-4 methyl branched tridecyl-alcohol known for its use in lubricants and in those detergent formulations which do not require rapid biodegradation. This is because EXXAL® 13 only slowly biodegrades. While such a high amount of branching is not necessary, it would be desirable to make a surfactant having a higher amount of branching for detergency which is nevertheless readily biodegradable.
U.S. Pat. No. 5,196,625 describes a dimerization process for producing linear and/or mono-branched C10 to C28 olefins using dimerization catalysts, for the production of biodegradable alkylbenzene sulfonates detergents by alkylating the olefins onto benzene. No mention is made of using the dimerized olefins to make alcohols. Further, the patentee reported that it is generally recognized that “linear and mono-branched alkyl aromatic sulfonates are generally much more readily biodegraded than multibranched alkyl aromatic sulfonates and, hence, much more desirable as detergents.” For this reason, the patentee sought to ensure that the olefins made were substantially linear and monobranched. Again, it would be desirable to make highly branched products that have good detergency and biodegradability from alcohols, and also without regard to limitations on the amount of branching being low.
The patentee of U.S. Pat. No. 4,670,606 likewise recommended using “linear detergent oxo-alcohols or those in which the linear fraction is as high as possible” for biodegradability reasons in the detergent field, while oxo-alcohols that are highly branched are desirable as lubricating oil additives because the branching depresses the freezing point of the lubrication oil. Thus, the invention was directed towards methods to separate the two from a mixture.
The desire to make highly linear high olefin alcohols was also expressed in U.S. Pat. No. 5,488,174. In discussing the problems encountered by cobalt carbonyl catalyzed hydroformylation of olefins, the patentee noted that this process produced a composition which contained branched compounds when starting with internal olefins, which was particularly undesirable because of its poor biodegradability. Thus, the patentee recommended using catalytic processes which would produce mixtures exhibiting high linear/branching ratios.
As previously noted, the highly linear NEODOL® alcohol line of intermediates for the production of detergent surfactants are commercially successful, in part, because of their high linearity rendering them readily biodegradable. However, the high degree of linearity also increased the hydrophobicity of the hydrophobe part of the chain, thereby decreasing its cold water solubility/detergency. In general, the highly linear alcohol sulfates suffer from poor cold water solubility/detergency. Along with the concern for using biodegradable compounds, government regulations are also calling for the lowering of wash temperatures.
Thus, there exists a growing need to find alcohol intermediates which are both biodegradable and exhibit good detergency at cold wash temperatures. The solution to this problem was not merely as simple as increasing the branching of the higher olefin alcohol in order to decrease hydrophobicity and thereby hopefully increase cold water detergency, because, as noted above, it is well recognized that branched compounds exhibit poor biodegradability.